Lawrence Berkeley National Laboratory

We present a novel linear scaling ab initio total energy electronic structure calculation method, which is simple to implement, easily to parallelize, and produces essentially the same results as the direct ab initio method, while it could be thousands of times faster. Using this method, we have studied the dipole moments of CdSe quantum dots, and found both significant bulk and surface contributions. The bulk dipole contribution cannot simply be estimated from the bulk spontaneous polarization value by a proportional volume factor. Instead it has a geometry dependent screening effect. The dipole moment also produces a strong internal electric field which induces a strong electron hole separation.